Method and device for feeding a sheet metal panel to a punch press
The procedure followed for aligning a metal sheet in the correct position for inserting it into a punch press is that the aligned position in the feed direction is adjusted by means of stops. The alignment in the second direction orthogonal to the feed direction is such that the position of the metal sheet in the second direction is determined by a sensor and a control unit, and the deviation of the metal sheet from the predetermined aligned position in the second direction from the control unit is determined. Next, the alignment in the second direction is controlled by means of the gripping arrangement which is provided for the feed of the metal sheet to the punch press by controlling the gripping arrangement in such a way that the deviation is compensated and the metal sheet is aligned correctly.
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This application is a National Stage application of International Patent Application No. PCT/CH2017/000033 filed Apr. 4, 2017, which claims priority to Swiss patent application No. 00591/16, filed May 4, 2016, each of which is hereby incorporated by reference in its entirety.
FIELD OF THE INVENTIONThe invention relates to a method for aligning a metal sheet in feeding the metal sheet to a processing station, in particular to a punch press, wherein the feed toward and into the processing station takes place in a first direction (Y axis) of two orthogonal directions (X axis and Y axis), wherein the alignment of the metal sheet takes place by a first alignment step in the first direction (Y axis) and, in a second alignment step, the alignment takes place in the second direction (X axis), in order to achieve a predetermined aligned position of the metal sheet, and wherein, for feeding the metal sheet, the sheet is gripped by a gripper arrangement, conveyed toward the processing station and introduced into the processing station, where it is punched to produce the desired processing pattern, in particular a punch pattern, and where it is preferably additionally conveyed back and forth in the second direction. Furthermore, the invention also relates to a device for carrying out the method and a system for producing punched parts using such a device.
BACKGROUND OF THE INVENTIONIn the metal packaging industry today, can lids or deep-drawn cans made of steel or aluminum, in round or non-round shape, are often produced on high-performance systems. For reasons of productivity, portal presses are used, enabling the use of multiple tools. Depending on the type of press and the available pressing force, tools in a “zigzag” or linear arrangement are used. With each press stroke, several components are thus produced at the same time. The basic material—whether made of aluminum or steel—is processed in the press in the form of metal sheets. By means of one or more gripper systems or rollers, the metal sheets are fed to the tools and then processed step by step. Depending on the type of tool and the feed system, the sheets are moved only in the Y direction or in the X and Y directions in an orthogonal coordinate system. Again, sheets as large as possible are processed for reasons of productivity. When larger sheets are used, there are fewer sheets that must be lacquered, cut, fed, etc. In any case, however, the metal sheets must be brought into each punch position with a high precision.
The metal sheets are fed to the system in the form of a stack. Several thousand metal sheets may be stacked in a stack. Weight usually limits the height of the stack. The stacks are placed on a chain conveyor or a roller conveyor and then conveyed either in the production direction of the metal sheet processing in the press or in a direction 90° to the production direction into the stacking and destacking position. An electrically or hydraulically driven lift system lifts the stack up to a vertical position, in which the metal sheets are gripped individually and fed in the direction of the sheet press.
Because of the great weight of the stack (usually several tons), the stacks can be guided into the destacking position only with a relatively great inaccuracy. Consequently, the destacking position may vary as much as a few centimeters from one stack to the next. Furthermore, the stacks often have stacking errors. The metal sheets may be displaced (fanned out) either in the stacking operation in the coil cutting system or in the lacquering system or during conveyance to the processing system. Modern destacking systems today must be capable of compensating for such errors. However, more accurate centering of the stack would require complex and expensive mechanisms. Furthermore, the process of destacking each individual sheet by using suction grippers is also relatively inaccurate. When the metal sheets are gripped and conveyed in the direction of the sheet press, the sheets may as well be oiled. Rollers, which can cause additional inaccuracies in the lateral position of the sheets, are generally used for this oiling process.
Before a metal sheet fed to the punch press can be processed in the pressing tool, it must thus be brought into a defined precise position by an aligning arrangement. This is true in the feed direction to the punch press as well as in the direction perpendicular thereto. The precision must be in the range of ±0.2 mm. One reason for this is that the various punch positions in the metal sheet should be as close together as possible, so that maximum utilization of material of the metal sheet is achieved. Additional reasons may include the fact that the sheets may be lithographed (printed) and the punching must correspond precisely to the printing or that the residual web width at the edge of the sheet should be kept very small. This is an important criterion in processing metal sheets on a sheet press with a multiple tool to achieve a high productivity.
DE 43 45 184 A1 discloses a centering mechanism by which a centering station, referred to here as an alignment station, for metal sheets is designed with two lateral stops and a rear stop for the metal sheets.
As soon as a metal sheet has reached its definitive orientation and position and/or is aligned correctly, it is taken over by a handling system and conveyed for processing in the tool 20.
The alignment and/or centering mechanism according to the prior art, as explained here, is complex and requires high maintenance. Furthermore, this mechanism needs a certain amount of time in order to align the sheets. During the centering and/or alignment operations, the handling system and/or the gripper cannot yet receive the metal sheet—first, because the alignment is not yet completed, and second, because the alignment mechanism could cause a collision with the gripper.
SUMMARYThe object of the invention is to provide an improved method for alignment of a metal sheet upon feeding the metal sheet to a processing station. In particular, a reduced need for maintenance and a more rapid conveyance to the press are to be made possible with this invention.
This object is achieved for the method defined in the introduction by that the alignment of the metal sheet in the second direction (X axis) is done by the following steps:
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- determining the position of the metal sheet in the second direction (X axis) by at least one sensor means;
- detecting the deviation of the metal sheet from its predetermined aligned position in the second direction by analyzing the sensor signals using a control unit; and
- correcting the deviation of the aligned position from the predetermined aligned position in the second direction (X axis) after gripping of the metal sheet by means of the gripping arrangement, in that the gripping arrangement provides, in a process controlled by the control unit, the movement of the metal sheet into the predetermined aligned position in the second direction during the feed movement of the metal sheet to the processing station.
The subject matter of the invention is thus to omit the sheet metal displacement in the X axis or the second direction, respectively, as a separate alignment step. Instead, the position of the sheet in the X axis is detected by at least one sensor, preferably in a noncontact detection operation, so that this position can be detected in a control unit connected to the sensor. Thus, instead of bringing the sheet first into a defined X position and then transferring the sheet to the gripper arrangement, first only the X position of the metal sheet is detected. The control unit calculates the taking over position for the gripper arrangement on the basis of the values thereby obtained and the gripper arrangement brings the metal sheet into the correct position with respect to the X axis or, in other words, compensates for the deviation found by the sensor device and the control unit from the predetermined aligned position in the second direction upon feeding the metal sheet to the processing station. Therefore, no alignment parts for the alignment in the X axis must be adjusted or maintained.
The advantage of this procedure is thus, on the one hand, the elimination of the complex and high-maintenance alignment mechanism. On the other hand, the time required for this mechanism to align the sheet is also omitted.
Before the sheet is gripped, the position of the gripper arrangement is preferably adapted to the deviating position of the sheet in the X direction by displacing the gripper arrangement accordingly. Thus, the sheet is gripped in the position on the metal sheet provided for this purpose.
The position of the sheet in the second direction is preferably determined by a stationary sensor, which yields a simple and robust design. Alternatively or additionally the position may be determined in the second direction by a movable sensor, in particular by arranging a sensor on the gripper arrangement and having the latter move the sensor over the metal sheet. In this way, it is possible to use a movable sensor, which can simplify the design of the sensor that is used without requiring any additional mechanism for the movement of the sensor.
In particular, a line sensor with or without a reflector or a camera with image processing may be used as the sensor for the sensor means. The sensor may be arranged above or beneath the position of the metal sheet or a sensor may be provided both above and beneath the position of the metal sheet. Multiple sensors in all the variants described here can improve the detection of the position, in particular with the preferred use of optical sensors of the sensor means because the metal sheets may have different reflection properties depending on the material and the pretreatment. Instead of noncontact optical sensor means, however, sensor means that operate by touch may also be used.
The present invention is additionally based on the object of creating an improved device for alignment of a metal sheet in feeding the metal sheets to a processing station, in particular to a punch press. In particular, a lower need for maintenance and a more rapid feed to the processing station and/or press should be made possible with this device.
This object is achieved with a device having a gripping arrangement gripping the metal sheet and moving the metal sheet into a predetermined position aligned with the processing station.
The subject matter of the invention is thus also to avoid by this device the displacement of the metal sheet in the X axis or in the second direction, respectively, as a separate alignment and instead to make the position of the sheet in the X axis detectable by at least one sensor so that this position can be determined in a control unit connected to the sensor. Thus, instead of bringing the sheet first into a defined X position and transferring the sheet then and only then to the gripper arrangement, this makes it possible for the device to first detect only the X position of the metal sheet. The control unit then calculates the taking over position for the gripper arrangement on the basis of the values thereby obtained, and the gripper arrangement brings the metal sheet into the correct position with respect to the X axis upon feeding the metal sheet to the processing station. Thus, no alignment parts for alignment in the X axis need to be adjusted and maintained with this device.
Thus, on the one hand, the advantage of this device is to eliminate the complex and high-maintenance alignment mechanism, but on the other hand, the time required by this mechanism to align the sheets is also eliminated.
It is preferable to provide a stationary sensor for determining the position in the second direction, which yields a particularly robust and maintenance-free device. It is also possible to provide a movable sensor of the sensor means for determining the position in the second direction, in particular it is possible for the sensor of the sensor means to be arranged on the gripper arrangement and to be movable by means of this configuration over the metal sheet, which has the advantage that it is not necessary to use any additional mechanism for the movement of the sensor because the gripper arrangement is designed anyway for carrying out the required movement.
In particular a line sensor with or without a reflector may be provided as the sensor or a camera with image processing may be provided as the sensor. Furthermore, the sensor means may also include sensors arranged above or below the position of the metal sheet. These measures and/or types and arrangements of sensors can improve the detection of the edges of the metal sheet in an industrial environment. In particular it may therefore be advantageous to provide sensor means having a plurality of different sensors for detecting the position of the metal sheets.
In addition, the invention is based on the object of providing an improved system for producing punched parts for metal sheets.
This object is achieved with a system having a sheet metal destacker, a punch press and a device for aligning the metal sheets with the punch press while feeding the metal sheets to the punch press.
Thus, with this invention in all its embodiments, the procedure followed in feeding a metal sheet to a punch press for alignment of the metal sheet in the correct position for inserting the metal sheet into the punch press, is such that the aligned position is adjusted by means of stops in the feed direction. The alignment in the second direction orthogonal to the feed direction is accomplished in such a way that the position of the metal sheet in the second direction is determined by at least one sensor and a control unit, and the deviation of the metal sheet from the predetermined aligned position in the second direction is determined by the control unit. Then the alignment in the second direction is accomplished by means of the gripper arrangement, which is present for feeding the metal sheet to the punch press, in that the gripper arrangement is controlled in such a way that the deviation is compensated and the metal sheet is aligned correctly.
Additional embodiments, advantages and applications of the invention are derived from the dependent claims and from the description which now follows with reference to the figures, in which:
To illustrate an exemplary embodiment of the invention, reference is also made to the coordinate system according to
In the figures in the exemplary embodiment, the sensor means 16 comprise at least one stationary sensor 17 with a longitudinal extent in the X coordinate direction. This sensor is, for example, a line sensor having a plurality of light-sensitive sensor elements arranged in a row and thus capable of emitting a signal which can determine the position of an object above the sensor, by detecting which sensor elements are darkened by the object and which sensor elements are not darkened. In this example, such a sensor is arranged in a recess 13 in the tabletop, so that it comes to lie beneath the metal sheet 1. Furthermore, it is arranged in such a way that, with the metal sheet 1 aligned in the Y coordinate, the position of the edge 1′ in the X coordinate can be emitted as a sensor signal via the sensor. It can be seen in
The sensor means may also include detection of the sheet metal edge by means of at least one movable sensor instead of at least one stationary sensor or in addition to a stationary sensor. For example, as shown in
At any rate, the sensor means may also comprise a sensor that is movable separately from the gripper. For example, a movable proximity switch may be provided. In this case detection of the sheet metal edge may take place by means of a time calculation. Since the starting position of the sensor is known and the rate of movement of the sensor is known, the time at which the sensor detects the edge of the sheet metal can be determined. An accurate position can be deduced from this time. However, to eliminate maintenance, sensor means which operate with a stationary sensor or with a stationary camera or with a movable sensor arranged on the gripper or with a camera arranged on the gripper are preferred.
Due to the determination of the position of the metal sheet in the second direction (X axis) by the sensor means 16 and detection of the deviation of the metal sheet from its predetermined aligned position in the second direction by analysis of the sensor signal by the control unit, the deviation can be corrected subsequently in feeding and/or transporting the metal sheet to the press.
The correction of the deviation of the aligned position from the predetermined aligned position in the second direction (X axis) takes place after the metal sheet has been gripped by means of the gripping arrangement in that the gripping arrangement executes the movement of the metal sheet into the predetermined aligned position in the second direction during the feed movement of the metal sheet to the processing station, controlled by the control unit. This may take place in such a way that the gripper arrangement with the gripper 11, which is known to be movable by the control unit in X and Y directions, can be moved by means of corresponding drives of the gripper, first executes a movement in the X− (Xminus) direction to correct the amount ΔX and then executes the movement toward the press 20 in the direction Y+. However, a combined X and Y movement of the gripper 11 is preferred so that it is moved in the direction of the arrow K wherein the movement in the direction X− takes place only as long as the deviation ΔX has been eliminated.
It is preferable for the location of the gripper arrangement to be adapted to the recognized location of the sheet, which deviates in the second direction before the gripping of the sheet by displacing the gripper arrangement accordingly in two directions in order to provide the gripping of the sheet in the location on the sheet provided for this purpose. This is shown in
Then the gripper 11 brings the metal sheet into the press 20 and carries out the known punching movement in X and Y directions, as shown in
Although preferred embodiments of the invention are described in the present patent application, it should be pointed out clearly that the invention is not limited to them and can also be carried out in another way within the scope of the following claims.
Claims
1. A method for aligning a metal sheet upon feeding the metal sheet to a processing station, wherein the feed takes place in a first direction (Y axis) of two orthogonal directions (X axis and Y axis), wherein in a first alignment step, the alignment of the metal sheet takes place in the first direction (Y axis) and in a second step the alignment takes place in the second direction (X axis) to achieve a predetermined aligned position of the metal sheet, and wherein for feeding the metal sheet is gripped by a gripper arrangement and is moved towards the processing station and introduced into the processing station and is additionally moved back and forth in the second direction for achieving the desired processing pattern, wherein the alignment of the metal sheet in the second direction (X axis) is provided by the following steps:
- determining the position of the metal sheet in the second direction (X axis) by a sensor means;
- detecting the deviation of the metal sheet from its predetermined aligned position in the second direction by analyzing the sensor signal by a control unit;
- adapting the position of the gripping arrangement to the detected position of the sheet to eliminate the detected deviation by displacing the gripping arrangement in the second direction according to the deviation and the detected position of the sheet before gripping of the sheet at the sheet's determined position for movement in the second direction; and
- correcting the deviation of the aligned position from the predetermined aligned position in the second direction (X axis) after gripping the metal sheet by means of the gripping arrangement, in that the gripping arrangement, controlled by the control unit, performs the movement of the metal sheet into the predetermined aligned position in the second direction in combination with the feed movement of the metal sheet to the processing station.
2. The method according to claim 1, wherein the step of determining the position of the metal sheet in the second direction is determined by a stationary sensor of the sensor means.
3. The method according to claim 1, wherein the step of determining the position of the metal sheet in the second direction is determined by a movable sensor of the sensor means.
4. The method according to claim 3, wherein the movable sensor is arranged on the gripping arrangement and is moved by the gripping arrangement over the metal sheet.
5. The method according to claim 1, wherein a line sensor with or without a reflector is a sensor of the sensor means and/or a camera with image processing is a sensor of the sensor means.
6. The method according to claim 1, wherein a sensor of the sensor means is arranged above or below the position of the metal sheet or a sensor of the sensor means is provided both above and below the position of the metal sheet.
7. The method according to claim 1, wherein the position of the metal sheet is detected on one edge or on the other edge of the metal sheet which lies in the X direction.
8. The method according to claim 1, wherein the position of the metal sheet position is detected by several different optical sensors of the sensor means.
9. A device for alignment of a metal sheet upon feeding the metal sheet to a processing station comprising: a control unit and a gripping arrangement with at least one gripper, said gripping arrangement being provided to implement feeding of the metal sheet, under control by the control unit, to the processing station, in a first direction (Y axis) of two orthogonal directions (X axis and Y axis), and being additionally provided for the movement of the metal sheet in the second direction; sensor means connected to the control unit and producing a sensor signal indicating the position of the metal sheet in the second direction (X axis), and the control unit being adapted to determine from the sensor signal the deviation of the metal sheet from a predetermined aligned position in the second direction, and cause the gripping arrangement to be displaced in the second coordinate direction before gripping the metal sheet to compensate for any deviation of the metal sheet from the predetermined aligned position, and then grip the metal sheet and execute movement of the metal sheet into the predetermined aligned position in the second direction during the feeding movement of the metal sheet to the processing station.
10. The device according to claim 9, wherein the sensor means for determining the position in the second direction is a stationary sensor.
11. The device according to claim 9, wherein the sensor means is a movable sensor for determining the location in the second direction.
12. The device according to claim 11, wherein the movable sensor of the sensor means is arranged on the gripping arrangement and can be moved by it over the metal sheet.
13. The device according to claim 9, wherein the sensor means is a line sensor with or without a reflector, or a camera with image processing.
14. The device according to claim 9, wherein the sensor of the sensor means is arranged above or below the metal sheet position, or the sensor means is comprised of sensors above and below the metal sheet position.
15. The device according to claim 9, wherein sensor means has a plurality of different sensors for detecting the metal sheet position.
16. A system for producing punched parts from metal sheets, the system including a destacker for destacking individual metal sheets from a stack, a punch press for forming the punched parts from the respective metal sheet and having a device according to claim 9 for aligning the respective metal sheets upon feeding them to the punch press.
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Type: Grant
Filed: Apr 4, 2017
Date of Patent: Aug 4, 2020
Patent Publication Number: 20190143391
Assignee: SOUDRONIC AG (Bergdietikon)
Inventors: Reto Walti (Widen), Roland Dietschi (Mellingen)
Primary Examiner: Lynn E Schwenning
Application Number: 16/098,281
International Classification: B21D 43/02 (20060101); B21D 28/04 (20060101); B21D 43/10 (20060101); B21D 43/24 (20060101);